下面是一个示例文件test.txt

hello world example
this is sample text

你可以尝试这样的方法：

$firstWord = "world"
$lastWord  = "sample"

# in keeping with your example:
@{n="charBetween";e={
  # Get raw content for a single string instead of per-line
  $text = Get-Content $_ -Raw

  # index of first and last words
  $i1 = $text.IndexOf($firstWord) + $firstWord.Length  
  $i2 = $text.IndexOf($lastWord) - 1

  # return -1 if one of the words was not found
  if ($i1,$i2 -eq -1) { return -1 }

  # output count each character between words
  else { $text[$i1..$i2].Count }
}}

# returns like this:

charBetween
-----------
18

请注意，Get-Content -Raw包含换行符，因此如果包含多行，则计数会稍高。